1. Technical Field
The present invention relates to a printing apparatus.
2. Related Art
As the printing apparatus, an ink jet printer is known, which forms an image on a printing medium by discharging an ink from a head.
As an example of such an ink jet printer, there is a printer that performs printing using colored inks such as CMY and a non-colored transparent ink (clear ink).
JP-A-2002-307755 is an example of the related art.
Here, there is a case in which a film-based medium that is configured from polystyrene, polypropylene or the like is used as the printing medium. In regard to the film-based medium, there is a case in which a charge is generated on the medium surface due to friction and the like between the film-based medium and a paper feed roller, which is formed from a metal (aluminum, steel or the like), within the printer. The amount of charge is influenced by the state of the friction; therefore, there is variation on the medium surface.
When the ink is discharged onto the printing medium in which there is variation in the amount of charge, an ink mist (so-called satellites) which is generated together with the discharging accumulates in a region at which the amount of charge is great. As a result, there is a case in which hazy image degradation occurs in the printed object.
On the other hand, it is possible to reduce the amount of charge to be substantially uniform by applying a supplementary ink such as a clear ink to the entire printing medium in advance.
However, the amount of charge differs depending on the environment (for example, a difference in moisture). In other words, even when using the same film-based medium, the degree of influence received from satellites (the degree of image degradation) is not fixed. Therefore, even when using the film-based medium, there is a case in which it is not necessary to use the supplementary ink.